SCI Q4: MUTATIONS

• Changes in the nucleotide/base sequence of DNA

  MUTATION
• condition when a cell or organism has one or more than one comple set of chromosomes

  EUPLOIDY
• condition in which a person has one or a few chromosomes above or below the normal chromosome number.

  ANEUPLOIDY
• • •Failure of chromosomes to separate during meiosis. •Causes gamete to have too many or too few chromosomes.

  NON- DISJUNCTION
• •It changes the structure of whole chromosomes

  CHROMOSOMAL STRUCTURE OF CHROMOSOMES
• Genetic disorder that involves delition of chromosomes

  cri-du-chat syndrome
• Effect of base duplications depend on location within the chromosome – whether or not duplication resides in coding or non-coding region of DNA

  duplications within the chromosomes
• a disorder which is the effect of the duplication of chromosomes

  Pallister-Killian mosaic syndrome
• Can be caused due to abnormal synapsis event at Meiosis I by incorrect chromosomes coming together. Associated with 2 forms of leukemia – oncogenes translocated to incorrect regions within chromosomes of leukocytes (white blood cells)

  translocation of chromosomes
• •affect single sites on DNA •If purine (A/G) or pyrimidine (T/C) substitutes for itself = transition substitution •If purine substitutes for pyrimidine or vice versa = transversion substitution

  I. point mutations
• results of point mutation

  •Silent Mutation •Missense Mutation •Non-sense Mutation
• no change in amino acid is produced

  SILENT MUTATION
• Produces a change in amino acid sequence in protein

  MISSENSE MUTATION
• Bad news!- produces stop codon within the mRNA transcriptsleading to a translocated protein

  NON-SENSE MUTATION
• •INSERTION or DELETION of one or more nucleotides. •Changes the “reading frame” like changing a sentence. •Proteins built incorrectly.

  II. Frameshift Mutations
• •If no changes to genomes occur over time, there would be no evolution

  true
• • Too much change in the DNA is harmful.

  true
• what causes mutations?

  The more contact a person has with mutagens, the higher the risk for cancer
• *A mutation can be inherited, caused by environmental agents, or happen spontaneously Mutagen – anything environmental that can cause a change in DNA

  true
• But mutations are not always harmful.

  true
• Mutations create different versions of alleles, which are alternative versions of the same gene.
• Genetic variation is important for evolution.